Thanks for replying folks ... yes, the petal shape is very watsonia like ... I found this image on google of Watsonia 'snow queen' which might be them ...

only for some reason the web site seems to be down right now.

Only thing is these don't seem very big compared to other watsonias (ours only got to 30-40cm, but were in shady spot), and the veining on the petals and buds is quite distinctive and I have not seen it in other watsonia pics.

No, not a Watsonia "Snow Queen" ... I'm beginning to think it's a Sparaxis bulbifera of some kind ... it has the same flower structure and does not grow as high as Watsonia do ... although I cannot find an example with the same distinctive petal veining as ours (and the ones I have seen around Wentworth Falls and Katoomba) ...